These tests were skipped due to compilation problems, but do now fully
pass on SwiftShader ES2.

Remove PointSpritesTest.PointWithoutAttributesCompliance/*
Remove ExplicitContextTest.GetProcAddress/*
Remove RobustBufferAccessBehaviorTest.EmptyBuffer/*
Remove EGLSyncTest.AndroidNativeFence_WaitSync/*

Bug: angleproject:5721
Change-Id: I3f50272c69ba78e2432f4278753e5d48d8601910
Reviewed-on: https://chromium-review.googlesource.com/c/angle/angle/+/2739723
Commit-Queue: Jamie Madill <jmadill@chromium.org>
Reviewed-by: Cody Northrop <cnorthrop@google.com>
Reviewed-by: Jamie Madill <jmadill@chromium.org>